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Objectives and questions: Human rib cartilage has demonstrated osteoconductive and osteoinductive properties, making it a potential alternative to traditional bone grafts. This study aims to evaluate the osseointegration, mineralization, and remodeling capacity of decellularized and MSC-recellularized human rib cartilage xenografts in a rabbit model. The key questions include: 1) Does recellularization with mesenchymal stem cells (MSCs) enhance mineralization and bone formation? 2) How does vascularization differ between decellularized and MSC-recellularized grafts? 3) Can human rib cartilage serve as a viable bone substitute in skeletal defect reconstruction?

Material and methods: Human rib cartilage from cadaveric donors was decellularized and either left acellular or recellularized with MSCs before implantation. Thirty New Zealand White rabbits underwent bilateral osteochondral defect creation and received either decellularized or MSC-recellularized grafts, while an empty defect group served as a control. At 4 and 12 weeks, histological (Movat Pentachrome, Von Kossa), immunohistochemical (osteocalcin, TRAP, α-SMA), and histomorphometric analyses were performed. Total ossified tissue (TOT), osteoid formation, vascularization, and osteoclast activity were quantified, and statistical analysis (ANOVA, Spearman correlation) was conducted.

Results: At 4 weeks, vascularization was highest in MSC-recellularized grafts (10 vessels/field) compared to decellularized grafts (9 vessels/field, p<0.05) and controls (3 vessels/field). By 12 weeks, vascularization decreased, with decellularized grafts retaining more vessels (4 vessels/field) than recellularized grafts (2 vessels/field). Histomorphometry revealed higher osteoid deposition in recellularized grafts (72.1% ± 4.2%) than in decellularized grafts (59.4% ± 5.1%, p<0.05). While early osteocalcin expression was greater in decellularized grafts, mineralization at 12 weeks was significantly higher in MSC-recellularized grafts (27.4% ± 3.7%) compared to decellularized grafts (19.8% ± 2.9%, p<0.01). TRAP staining showed higher osteoclast activity in recellularized grafts at 4 weeks (16 osteoclasts/field) than in decellularized grafts (12 osteoclasts/field), indicating increased remodeling. By 12 weeks, osteoclast activity declined in both grou

Discussion and conclusions: Both decellularized and MSC-recellularized rib cartilage grafts supported osseointegration, vascularization, and remodeling. However, MSC-recellularized grafts exhibited significantly superior mineralization and osteoinductive effects, suggesting their potential as an alternative to iliac crest bone transplants. These findings indicate that rib cartilage xenografts may be beneficial for non-load-bearing bone defects. However, rectifying the type of cartilage is still under investigation.